"IGCAR plans to deliver the next two fast breeder reactors incorporating the necessary design changes that reduce the material cost without compromising on performance, safety and other aspects," its director P.R. Vasudeva Rao said.

A fast-breeder reactor breeds more material for a nuclear fission reaction than it consumes. It is the key to India's three-stage nuclear power programme. IGCAR is tasked to design fast reactors and also carry out relevant research activities.

The first fast reactor designed and developed by IGCAR, a 500 MW prototype fast breeder reactor (PFBR), coming up at Kalpakkam, is expected to go on stream next year.

"The PFBR reactor has 850 tonnes of stainless steel. The total steel content is around 1,300 tonnes. In the next two reactors, the metal content will be 25 percent less. The changes will also reduce construction time," P.Chellapandi, director of IGCAR's Reactor Design Group, said.

"The design for next two units has been finalised and is being reviewed," he added. According to him, the reactor safety has been further enhanced by adding passive safety features.

The PFBR and the two more reactors will be powered by a blend of plutonium and uranium oxide fuel, also called MOX fuel. "We have decided to limit MOX fuel reactors to three units. We may build metallic fuel reactors instead of two more MOX fuel reactors planned earlier," Ratan Kumar Sinha, secretary of the department of atomic energy and chairman, Atomic Energy Commission, said.

Metallic fuel has a better breeding ratio as compared to MOX fuel.

"The idea is to switch over to metallic fuel reactors at the earliest. After three fast breeder reactors, we may take stock of the situation and decide whether to go for metallic or MOX fuel reactors," Rao added.